Device for extracorporeal blood treatment

ABSTRACT

The invention relates to a system for treating blood, which includes a single cassette capable of carrying out the various CRRT treatments.

The present application is a divisional application that claims priorityto application Ser. No. 14/439,382 filed on Apr. 29, 2015, which is theUnited States national stage application of International patentapplication PCT/IB2013/059744 filed on Oct. 29, 2013 designating theUnited States, and claims foreign priority to International patentapplication PCT/IB2012/055972 filed on Oct. 29, 2012, the contents ofeach of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The invention relates to a device for extracorporeal blood treatment.The device comprises in particular a cassette permitting thedistribution of the fluids in order to carry out said treatment, andmeans for improving the efficacy of said device that can be usedseparately and/or with said cassette.

PRIOR ART

There are several possible reasons why a person may suffer from renalinsufficiency, in which the temporary/permanent and partial/totalshutdown forces this person to use extracorporeal devices thatcompletely or partially replace the patient's own kidneys. Dialysis is atechnique of blood purification. It allows a patient suffering from sucha disease to eliminate impurities such as urea and excess water from theorganism, which would usually have been eliminated by normallyfunctioning kidneys.

It is possible to differentiate between two types of renal insufficiencylinked to the duration of the disease and sometimes requiringconsiderably different treatments, i.e. chronic renal insufficiency andacute renal insufficiency. Chronic renal insufficiency means that thepatient has to undergo treatment at regular intervals for life. For thispurpose, the patient can carry out this treatment at a medical center orat home using an apparatus for peritoneal dialysis or hemodialysis.Acute renal insufficiency is a temporary disease in which the patientrequires an apparatus to temporarily replace the functions of hiskidneys. In this case, the patient undergoes continuous renalreplacement therapy. Peritoneal dialysis and continuous renalreplacement therapy are very different, as are the techniques and/ordevices used:

-   -   Peritoneal dialysis uses the patient's peritoneum, which is the        natural membrane enclosing the walls of the abdomen and the        organs situated in the abdomen (liver, intestines, etc.). The        peritoneal membrane has a very large surface area and comprises        a very large number of blood vessels. It thus performs the role        of natural filter. Numerous patents disclose systems for        carrying out peritoneal dialysis, some of which use cassettes        (EP 1 648 536 A2, EP 0 471 000 B1, EP 1 195 171 B1, EP 1 648 536        B1) for injecting fluid into the patient's peritoneum and        removing the fluid therefrom.    -   Continuous renal replacement therapy (CRRT) is a method in which        blood has to be removed continuously from the patient and        treated by means of a filter, generally a dialyzer, after which        the treated blood is re-injected into the patient. Two main        principles are used by virtue of the filter:        -   Diffusion allows solute molecules to pass through a            semipermeable membrane according to a concentration            gradient. The solutes pass from the more concentrated medium            (the blood) to the less concentrated medium (the dialysate)            and are distributed uniformly on each side of the membrane            of the filter.        -   Convection permits the simultaneous transfer of water and of            its solute content through the semipermeable membrane by            virtue of the hydrostatic pressure gradient across the            membrane. Thus, the solutes pass from the medium where the            pressure is highest (blood compartment) to the medium where            the pressure is lowest (dialysate compartment).

Various techniques of continuous renal replacement therapy exist thatuse one or both of these principles: slow continuous ultrafiltration(SCUF), continuous venovenous hemofiltration (CVVH), continuousvenovenous hemodialysis (CVVHD), continuous venovenous hemodiafiltration(CVVHDF), therapeutic plasma exchange (TPE) and hemoperfusion (alsocalled blood detoxification). At present, no device is able to provideall of these treatments without the intervention of trained medicalstaff. In addition, these techniques are mainly used in intensive careenvironments. Unfortunately, these techniques make use of cumbersomeappliances that can interfere with the proper conduct of othertreatments carried out on the patient. Moreover, these appliances arecomplex and comprise numerous consumables, and they require substantialchanges to be made in order to carry out the various techniquesmentioned above. This involves the personnel receiving special training.

General Description of the Invention

The invention relates to numerous improvements for medical devices,means and/or methods used for medical devices.

The present application claims the priority of the application bearingthe number PCT/IB2012/055972 filed on Oct. 29, 2012 in the name ofDebiotech, the entire content of which application must be regarded asforming part of the present application.

A first aspect of the invention relates to a single cassette by means ofwhich it is possible to carry out one or all of the various techniquesof continuous renal replacement therapy: slow continuous ultrafiltration(SCUF), continuous venovenous hemofiltration (CVVH), continuousvenovenous hemodialysis (CVVHD), continuous venovenous hemodiafiltration(CVVHDF), therapeutic plasma exchange (TPE) and hemoperfusion. In oneembodiment, the device can also be used in the context of peritonealdialysis, where some elements and/or features might not be used or couldbe used for other functions, such as taking samples or the like. In anembodiment, the cassette is partially or completely integrated in thedialysis apparatus, or some of these elements form part of saidapparatus (for example the pumping system, the sensors, the filter,etc.) or are physically separate from the cassette (for example thefilter, supply means, reservoirs, sensors, heating means, etc.) or areoptional. Preferably, said cassette and the dialysis apparatus are bothseparate. The cassette can be discarded whereas the apparatus can bereused. This means that the cassette can be replaced at each treatment(single use, replacement of the cassette after each use) and that theapparatus can be used several times with different cassettes. Saidcassettes are designed to cooperate physically and/or mechanically withthe apparatus and/or vice versa. In addition, the use of a singlecassette makes it possible to simplify the use of said device, to reduceoperator errors by virtue of this simplification, to automate thetreatment without the intervention of medical staff, to limit the numberof cassette types, to simplify programming, to permit the use of thedevice at the patient's home and/or to limit the space taken up by thedevice.

According to a second aspect of the invention, the device can compriseonly 3 main pumps in order to carry out at least one or all of thetechniques cited in the prior art (SCUF, CVV, CVVH, CVVHDF, TPE andhemoperfusion).

According to one embodiment, the device comprises a blood filtrationmeans, at least one liquid supply means, two patient tubes, namely anoutlet tube for collecting the blood to be treated, and an inlet tubefor re-injecting the treated blood into the patient, (or a single tubein the case of peritoneal dialysis or a tube with two separate lumens),a filtrate recovery means, three fluid pumps, a cassette composed ofchannels and valves for directing the fluids, and a controller whichcontrols the pumps and the opening and the closure of said valvesdepending on the desired treatment.

Said cassette comprises at least one distribution chamber comprising asingle inlet channel, at least two outlet channels and at least twoconnection chambers comprising at least two inlet channels and an outletchannel. Preferably, said distribution chamber comprises an inletchannel and three outlet channels controlled by the controller (in anautomatic, programmed and/or controlled manner) so as to allow a fluidto be injected into the blood filtration means, into the blood beforethe blood filtration means (pre-dilution) and/or after the bloodfiltration means (post-dilution). By virtue of this distributionchamber, the device can carry out any treatment by dialysis without themedical staff (or other specialists) being present in order to configurethe specific connections for each treatment.

Said system additionally comprises at least three flow paths. The firstflow path connects said blood filtration means to the filtrate recoverymeans. It comprises a series of channels and a dedicated pump. Thesecond flow path is dedicated to the circulation of the blood. Itcomprises at least two connection chambers, a series of channels, saidblood filtration means, said patient tubes and a dedicated pump. Thethird flow path comprises a liquid supply means, at least one dedicatedpump, a series of channels, a distribution chamber and, optionally, aheating means.

Said distribution chamber comprises at least three separate outletchannels:

-   -   a first outlet channel supplying the second flow path upstream        of the filtration means (for carrying out a pre-dilution of the        blood before it is filtered by the filtration means),    -   a second outlet channel supplying the second flow path        downstream of the filtration means (for carrying out a        post-dilution of the blood after it has been filtered by the        filtration means), and    -   a third outlet channel supplying said filtration means.

In one embodiment, the two connection chambers and the distributionchamber are supplied with positive pressure by two pumps that are placedupstream of said chambers.

Said first connection chamber makes it possible to connect the secondflow path to the third flow path upstream of the filter (pre-dilutiontechnique). It comprises an inlet channel coming from the second flowpath, an inlet channel coming from the third flow path, and an outletchannel allowing the blood to flow in the direction of the filter, andsaid inlet channel coming from the third flow path can comprise a valvecontrolled by said controller, a flow restrictor and/or a pump.

Said second connection chamber makes it possible to connect the secondflow path to the third flow path downstream of the filter (post-dilutiontechnique). It comprises an inlet channel coming from the second flowpath after its passage through the filter, an inlet channel coming fromthe third flow path, and an outlet channel in the direction of thepatient.

According to certain embodiments, the invention can additionallycomprise:

-   -   A supply means for injecting an anticoagulant into the second        flow path, either directly into the patient outlet tube, or        farthest upstream in the cassette by virtue of a connection        chamber that allows the anticoagulant to be mixed with the blood        (fluid of the second flow path), and/or    -   A supply means by which a product inhibiting the anticoagulant        is injected into the second flow path, either directly into the        patient inlet tube, or farthest downstream in the cassette by        virtue of a connection chamber that allows said product to be        mixed with the blood (fluid of the second flow path).

A third aspect of the invention relates to the structure of thecassette, when a flow path (coming, for example, from a liquid supplymeans) is connected to another flow path, the cassette preferablycomprises a connection chamber permitting the intersection of said twoflow paths. This connection chamber can thus permit mixing of the fluidscoming from said flow paths. In addition, at least one of said inletchannels of said connection chamber can comprise a valve, such that thecontroller can select the one or more defined fluids that will flow intothe connection chamber depending on the treatment that is desired,programmed or controlled.

According to a fourth aspect of the invention, a heating means issituated in the third flow path between the main pump of the dialysateand the distribution chamber. Said heating means is preferably aflexible bag supplied with positive pressure by said pump. In oneembodiment, a second pump is located between the distribution chamberand a connection chamber. Preferably, the distribution chamber isconnected to a first and second connection chamber. The first connectionchamber makes it possible to carry out a pre-dilution of the fluidflowing in the second flow path (that is to say dilution of the bloodbefore the filtering means), while the second connection chamber permitsa post-dilution of the fluid of said second flow path (that is to saydilution of the blood after the filtering means). The first pump is aprecision pump by which it is possible to know precisely the quantity offluid that will be mixed in the blood at pre-dilution and post-dilution.The second pump is located downstream of one of the two connectionchambers, while the other connection chamber or both connection chamberscan comprise a valve. This second pump is a distributor pump by which itis possible to distribute a defined quantity of fluid between the firstand second connection chambers. This type of system can comprise one ormore other connection chambers. Preferably, the system comprises apressure sensor, and the heating means can serve as temporary storagemeans.

To optimize the function of the treatment system, the invention likewisediscloses the following elements, which can be used with or without thecassette described above:

-   -   a means and a method for calibration of the pumps of the first        and third flow paths,    -   a pressure sensor offset from the flow path,    -   an energy-saving linear actuator,    -   a drive device used for the peristaltic pumps,    -   a means of damping the pressure peaks.

Means and Method for Calibration of the Pumps and/or Sensors of theFirst and Third Flow Paths:

In certain techniques of continuous renal replacement therapy, it isessential to know precisely the volume quantity injected into andwithdrawn from the third and first flow paths. The devices usuallycomprise two balances, namely a balance dedicated to the dialysate andanother one dedicated to the filtrate. The present invention cancomprise the same system of balances, but these balances are verysensitive and bulky (since they have to be able to contain all of thefluids). Other devices have cavities of which the volume capacity isknown with precision. These cavities are located directly on the firstand third flow paths (an intermediate wall being used so as not to mixthe two fluids) and they are successively filled with and then emptiedof the fluids of said flow paths. When the cavity fills with dialysate,the cavity empties itself of the filtrate previously contained in saidcavity and/or vice versa. These devices can comprise several of thesecavities. However, in contrast to the device of the present invention,these devices do not permit a continuous function, and instead theyfunction in a succession of steps of filling and emptying of the fluidscontained in said cavities.

According to a fifth aspect of the invention, the treatment system has ameans for calibrating said pumps in order to ensure that said volumesare known with precision. The system comprises:

-   -   at least two volume-measuring means (sensor, mass flow system,        volume pump, peristaltic pump, balance, etc.), of which one        measures the quantity of liquid flowing through the third flow        path, and one measures the quantity of liquid flowing through        the first flow path;    -   a means of taking samples from the first and third flow paths;    -   a common means of measuring the sampled volumes.

Said common measurement means measures the quantity of fluid sampled bythe sampling means and makes it possible to compare the sampled volumesand to calibrate said pumps and/or said volume-measuring means.

In one embodiment, said pumps are regarded as said volume-measuringmeans since each actuation corresponds to a given volume.

In another embodiment, the volume sensors are separate from the pumpsand continuously measure the volumes delivered by said pumps. In theevent of drifting of the pumped volumes, the controller is able tocorrect the actuation of said pumps in order to correct the volumes orthe volume differential.

A sixth aspect of the invention relates to a method for the calibrationof pumps used to deliver the fluids of the first and third flow pathsand/or of the sensors placed in said flow paths. The method additionallyallows said pumps to be calibrated before and/or during the treatment.

Pressure Sensor Offset from the Flow Path:

A seventh aspect of the invention relates to a means for measuring thepressure of a fluid. In one embodiment, the treatment system comprisesat least one pressure sensor in at least one of said flow paths. Thepresent document discloses a fluid distribution system (preferably acassette) which makes it possible to sample and/or deliver a fluid F11and to measure the pressure of said fluid F11. The system comprises arigid body composed of at least one flow path through which said fluidF11 flows, at least one channel separate from said flow path. Saidchannel makes it possible to connect said flow path to a measuring zone.The system can comprise at least one opening covered by a flexiblemembrane forming said measuring zone. The membrane is designed toreceive a pressure sensor.

A fluid F12 different than the fluid F11 is contained in said measuringzone. The fluid F12 at least partially fills the measuring zone and/orsaid channel. Said fluid F12 makes it possible to transmit the pressureof the fluid F11 to said membrane.

The aim of this channel is that the fluid F11 cannot come into contactwith said membrane or that the fluid F11 at least partially wets saidmembrane. Thus, the channel can be designed in such a way that saidfluid F11 limits, slows and/or controls the flow of the fluid F11through said channel. It has a shape and a length permitting thisfunction and/or can comprise a means for containing the fluid F11 (suchas a membrane, a hydrophilic filter, a hydrophobic filter, etc.).Preferably, the measuring zone is filled with both fluids F11 and F12and/or the fluids F11 and F12 are in contact with the membrane.

Energy-Saving Linear Actuator:

In one embodiment, the treatment system comprises at least oneenergy-saving linear actuator. The present document discloses aninnovative principle for controlling a linear actuator that consumes asmall amount of energy and for controlling the position of a valve. Thisactuator can be included in a system as described above, but also in anydevice using a linear actuator. In particular, the actuator must offertwo basic positions, namely valve closed (where the piston is in a firstposition) and valve opened (where the piston is in a second position).The piston can also have a third position corresponding to a state inwhich the piston of the actuator is disengaged from the foot of thevalve.

To ensure the function of linear actuator, two different techniques arenormally used: the electromagnet or the brushless motor mounted with anendless screw and a nut. The main disadvantage of these two techniquesis that they consume energy in order to maintain a position. The presentinvention discloses a linear actuator comprising at least two stationarypositions with low energy consumption and a rapid return to a safetyposition. In addition, the actuator disclosed by the present documentdoes not consume any energy, or only a small amount of energy, tomaintain its different positions.

The eighth aspect of the invention thus relates to a linear actuatorcomprising a rotary electric motor, a piston, and means which areinterposed between the electric motor and the piston and transform therotation movement of the motor into a linear displacement of the piston.Said interposed means comprise at least one peripheral ramp arrangedinside said piston, at least one guide means allowing the piston toguide the translation movement, and at least one bearing means fixeddirectly or indirectly to the rotor of said electric motor. Said bearingmeans is designed in such a way as to cooperate with said peripheralramp. In one embodiment, said actuator additionally comprises at leastone compression means that exerts a force against the piston in thedirection of the distal end of the piston. The ramp comprises at leastone threshold for obtaining at least one stationary position withoutconsuming energy. At least one threshold is positioned at the summit ofsaid ramp. In a preferred embodiment, this threshold is followed by apassage allowing the piston to free itself of the stresses exerted bythe bearing means.

According to a ninth aspect of the invention, the actuator is able toguarantee a given occlusion pressure when the valve is in the closedposition. The position of the valve with no contribution from theactuator is preferably a closed position. To guarantee good occlusion,the actuator has a compression means for ensuring a sufficient occlusionpressure of the valve against its seat when the piston is in the firstposition. Said compression means permits a third position (when thepiston is not engaged with the valve) in which the piston is locatedfarther away from the support of the actuator. The passage from thethird position to the first position is effected when the piston engageswith the valve. In other words, when the cassette is placed in thedevice. Thus, the compression means compels the piston to exert aninitial force against the valve, which transmits this force against theseat of the valve, guaranteeing an occlusion of the flow path when thepiston is in the first position.

In one embodiment, said compression means can be on the support of theactuator or in said piston. In other words, when said piston of theactuator is engaged with the foot of the valve, i.e. in the firstposition, a compression means ensures prestressing in order to guaranteegood occlusion. Said compression means can be mounted in the actuator oron the support of the actuator, said compression means making itpossible to obtain a third position in which the piston of the actuatoris farther from the support of the actuator than in the first and secondpositions. The occlusion pressure depends on the design of the valve andon the dimensions of the compression means.

Drive Device used for the Peristaltic Pumps:

A tenth aspect of the invention relates to a drive device used for apump.

During the use of said treatment system, the cassette is inserted in acycler which comprises sensors, linear actuators (for opening andclosing the valves), and means for driving the rollers of theperistaltic pump. In order to guarantee correct functioning of thesystem, it is important that all the elements are correctly aligned(sensor, actuator, actuation means, etc.). Now, there may be adifference between the theoretical central point of the head of the pumpand the actual central point. This difference creates problems in thealignment of the actuators and of the sensors, respectively, on thevalves and the measuring zones of the cassette. Thus, guide means makeit possible to overcome this problem of alignment for the sensors andactuators but transpose the difference to the pumping system. Thus,stresses of a greater or lesser degree may be exerted on the elements ofthe pump, which may affect the precision of the peristaltic pump. Thephenomenon is all the more pronounced when the pumps are present inlarge number.

In order to relax the manufacturing tolerances and to guarantee theprecision of the peristaltic pumps, the invention discloses a drivedevice for the pumps which comprises a floating shaft driven by a drivemeans fixed to a rotor. The floating shaft comprises a rigid assembly ofbase and cover that forms a cavity inside which said drive means is atleast partially circumscribed. In addition, said drive means comprises arigid body designed in such a way as to cooperate with the walls of saidcavity in order to permit a restricted freedom of the floating shaftwith respect to the shaft of said rotor. The floating shaft allows theaxis of the pumping system to be off-centered, so as to minimize or eveneliminate all stresses exerted by the shaft of the pump on thetheoretical pumping shaft of the cassette.

Means for Damping the Pressure Peaks:

An eleventh aspect of the invention relates to a means for damping thepressure peaks.

The quantity of a pumped fluid can be influenced by the constituentelements of the system. These elements can be the pumping mechanism, thevalve mechanism, the liquid supply means (tubes, reservoirs, etc.). Inparticular, the pumping mechanism of a peristaltic pump can causevariations in pressure. Thus, a pressure wave forms and spreads throughthe one or more flow paths each time the rollers come into contact withthe flexible tube. This spread is attenuated or reinforced by a numberof factors such as the type of liquid, the length of the flow path, therestrictions, the type of materials of the system, the quantity ofliquid delivered by the pumping mechanism, the type of pump, thecharacteristics of its components (flexible tube, etc.), the pressuredownstream of the pump, etc.

One of the improvements of the invention is to reduce the amplitude ofthe pressure peaks and the influence thereof on the quantity pumped.This reduction is achieved by adding to the flow path a means designedto absorb the pressure peaks.

Another advantage of this reduction of the peaks is likewise that ofobtaining a more constant pressure, which increases patient comfort. Inthis embodiment, the peaks can be damped downstream of the pump duringan injection toward the patient, and upstream when the pump withdraws afluid coming from the patient (in particular during peritonealdialysis).

This damping means can be a cavity filled with a compressible fluid suchas air. This damping means can be a flexible element that is deformed bythe pressure peaks and returns to a state of equilibrium. This flexibleelement can, for example, be a polymer membrane in the wall of the flowpath.

In the present document, the various aspects of the invention can be thesubject matter of independent or dependent claims which may or may notrelate to any system of medical treatment.

LIST OF FIGURES

The invention will be better understood below on the basis of a numberof illustrative examples. It goes without saying that the invention isnot limited to these embodiments.

FIG. 1 schematically depicts the blood treatment system disclosed by theinvention,

FIG. 2 schematically depicts the use of the cassette applying atreatment of slow continuous ultrafiltration,

FIG. 3 schematically depicts the use of the cassette applying atreatment of continuous venovenous hemofiltration,

FIG. 4 schematically depicts the use of the cassette applying atreatment of continuous venovenous hemodialysis,

FIG. 5 schematically depicts the use of the cassette applying atreatment of continuous venovenous hemodiafiltration,

FIG. 5′ schematically depicts another embodiment of the cassette,

FIG. 6 schematically depicts the use of the cassette applying atreatment of plasma replacement,

FIG. 7 schematically depicts the use of the cassette applying atreatment of hemoperfusion,

FIG. 8 schematically depicts the system with several liquid supplymeans,

FIG. 9 schematically depicts the system with a recirculation of thesecond flow path and reject,

FIG. 10 schematically depicts the system with the reference sensor,

FIG. 11 shows the rigid body of the cassette comprising a flow path andits channel for pressure measurement,

FIG. 12 shows the body of the cassette and the membrane that covers themeasuring zone,

FIGS. 13 and 13′ schematically depict the placement of the sensor offsetfrom a flow path,

FIG. 14 shows an exploded view of the linear actuator,

FIG. 15 shows a sectional view in which the valve is coupled to thestub/piston,

FIG. 16 shows two detailed views of the piston,

FIG. 17 shows two partially cutaway views of the piston in a thirdposition, valve (not shown) not coupled,

FIG. 18 shows two partially cutaway views of the piston in a firstposition, valve coupled (not shown),

FIG. 19 shows two partially cutaway views of the piston moving from thefirst position to the second position, valve coupled (not shown),

FIG. 20 shows the piston in a second position, valve coupled (notshown),

FIG. 21 shows the piston in a second position passing instantaneously tothe first position, valve coupled (not shown),

FIGS. 17′, 18′, 19′, 20′ and 21′ illustrate the cooperation between theramp and the bearing means driven by the motor (not shown),

FIG. 22 shows an exploded view of the drive device of the peristalticpump,

FIG. 23 shows a sectional view of the drive device of the peristalticpump,

FIG. 24 shows a graph of the pressure peaks caused by a pump,

FIGS. 25 and 26 show two different configurations of the shock-absorbingsystem,

FIG. 27 schematically depicts a minimal embodiment of the bloodtreatment system,

FIGS. 28 and 29 schematically depict more complex embodiments of theblood treatment system,

FIG. 30 illustrates a treatment system,

FIG. 31 schematically depicts the use of the additional pump fordistribution of the fluid,

FIGS. 32 and 32′ illustrate the use of a linear actuator,

FIG. 33 shows 3 graphs used by a system for actuator control.

REFERENCE NUMBERS USED IN THE FIGURES

-   1 patient-   2 cassette-   2′ cassette comprising the pumps-   3 blood filtration means-   4 heating means-   5 outlet tube from the patient-   6 inlet tube to the patient-   7 safety element-   8 entry of the blood into the filter-   9 entry of the dialysate into the filter-   10 exit of the filtrate from the filter-   11 exit of the blood from the filter-   12 membrane of the filter-   13 flow adjuster-   14 blood treatment system-   15 volume sensor of the third flow path-   16 reference volume sensor-   17 volume sensor of the first flow path-   100 fluid distribution system-   101 measuring zone-   102 channel-   103 flow path-   104 membrane-   105 rigid body of the cassette-   106 opening-   107 pressure sensor-   108 hydrophobic filter-   200 linear actuator-   201 DC motor with reducer-   202 rigid envelope-   203 groove in the rigid envelope-   204 sensor-   205 compression means-   206 magnet-   207 piston-   208 shaft of the motor-   209 transverse shaft-   210 element connecting the piston to the stub-   211 stub-   212 valve-   213 valve seat-   214 ramp-   215 threshold at the summit of the ramp-   216 guide means-   217 distal end of the piston-   218 proximal end of the piston-   219 passage-   220 direction 1-   221 direction 2-   300 drive device-   301 floating shaft-   302 cover-   303 drive means-   304 body of the drive means-   305 longitudinal shaft-   306 perpendicular shaft-   307 fastening screw-   308 hard elements-   309 and 309′ inner walls of the cavity-   310 rotor/motor-   311 base-   312 cooperation element-   313 cavity-   313′ second cavity-   320 roller-   321 shaft of the roller-   322 rigid part-   323 flexible part-   401 pressure curve-   402 mean pressure curve-   403 flexible membrane-   404 wall of the flow path-   405 compressible fluid (example gas)-   406 fluid-   500 patient-   501 1st chamber-   502 2nd chamber-   503 3rd chamber-   504 4th chamber-   505 5th chamber-   506 6th chamber-   507 1st pump-   508 2nd pump-   509 3rd pump-   510 4th pump (optional)-   511 5th pump (optional)-   512 6th pump (optional)-   513 filter-   514 1st fluid supply means-   515 2nd fluid supply means-   516 3rd fluid supply means-   517 fluid recovery means-   518 pressure sensor-   519 closure means (for example valve)-   520 flow-limiting means or closure means-   521 sensor-   522 heating means-   600 patient-   601 cassette-   602 dialysis apparatus/casing-   603 fluid supply means-   604 fluid recovery means-   605 processor-   606 sensors-   607 actuators (pump, valve, etc.)-   608 screen-   609 acquisition means and/or other, for example power supply means-   610 memory-   700 fluid distribution system-   701 main flow path-   702 precision pump-   703 flexible bag (for example flexible heating bag)-   704 and 704′ secondary flow path-   705 valve-   706 pressure sensor-   707 additional pump-   708 processor-   800 control system-   801 movable part of the actuator-   802 element 1 of the sensor-   803 element 2 of the sensor-   804 stationary part of the actuator-   805 control element (processor and/or other element)-   C1 first distribution chamber-   C1.1 supplementary connection chamber-   C1.2 supplementary distribution chamber-   C2 first connection chamber-   C3 second connection chamber-   C4 third connection chamber-   C5 fourth connection chamber-   C6 fifth connection chamber-   C7 second distribution chamber-   C8 sixth connection chamber-   C9 seventh connection chamber-   F1 first liquid supply means-   F2 second liquid supply means-   F3 third liquid supply means-   F4 filtrate recovery means-   F5 blood recovery or sampling means-   F11 fluid 1-   F12 fluid 2-   F13 fluid 3-   P1 pump of the second flow path (blood)-   P2 main pump of the third flow path (dialysate or substitution)-   P2′ additional pump of the third flow path-   P3 pump of the first flow path (filtrate)-   P4 pump of the second liquid supply means-   P5 pump of the third liquid supply means-   V1 inlet channel for blood in the third connection chamber-   V1′ inlet channel of the second liquid supply means in the third    connection chamber-   V1″ inlet channel for blood in the third connection chamber    originating from the second connection chamber-   V2 outlet channel for blood in the third connection chamber-   V3 inlet channel for blood in the first connection chamber-   V4 outlet channel for blood in the first connection chamber-   V5 inlet channel for dialysate or substitution product    (pre-dilution) in the first connection chamber-   V5′ outlet channel for dialysate or substitution product    (pre-dilution) of the supplementary distribution chamber (C1.2) to    the first connection chamber-   V6 outlet channel for dialysate or substitution product    (pre-dilution) from the first distribution chamber to the first    connection chamber-   V6′ outlet channel for dialysate or substitution product from the    first distribution chamber to the supplementary distribution chamber    (C1.2)-   V7 outlet channel for dialysate or substitution product from the    first distribution chamber to the filter-   V7′ outlet channel for dialysate or substitution product from the    first distribution chamber to the supplementary connection chamber    (C1.1)-   V7″ outlet channel for dialysate or substitution product from the    supplementary connection chamber (C1.1) to the filter-   V7′″ outlet channel for dialysate or substitution product from the    supplementary distribution chamber (C1.2) to the supplementary    connection chamber (C1.1)-   V8 outlet channel for dialysate or substitution product    (post-dilution) from the first distribution chamber to the second    connection chamber-   V9 inlet channel for dialysate or substitution product in the first    distribution chamber-   V10 outlet channel for blood to the patient-   V10′ outlet channel for blood to the third connection chamber-   V10″ outlet channel for blood to a recovery means-   V11 outlet channel for blood in the second connection chamber    originating from the filter-   V12 inlet channel for dialysate or substitution product    (post-dilution) originating from the first distribution chamber-   V12′ inlet channel of the third liquid supply means into the second    connection chamber-   V13 outlet channel for dialysate or substitution product-   V14 and V14′ inlet channel for dialysate or substitution product of    the first supply means-   V15 outlet channel for filtrate from the second distribution chamber    to the sixth connection chamber-   V16 outlet channel for filtrate from the second distribution chamber    to the seventh connection chamber-   V17 inlet channel to the seventh connection chamber originating from    the reference volume sensor-   V18 outlet channel for the volume to be measured-   V19 inlet channel in the sixth connection chamber for the volume to    be measured (dialysate)-   V20 inlet channel in the sixth connection chamber for the volume to    be measured (filtrate)

DETAILED DESCRIPTION OF THE INVENTION

In the present document, the detailed description of the inventionincludes embodiments of devices, systems and methods that are presentedby way of illustration. It will be appreciated that other embodimentsare conceivable and may be applied without departing from the scope orspirit of the invention. Therefore, the detailed description given belowmust not be taken in a restrictive sense.

Unless otherwise indicated, the scientific and technical terms used inthe present document have meanings currently used by a person skilled inthe art. The definitions given in this document are mentioned in orderto facilitate an understanding of the terms frequently used and are notintended to limit the scope of the invention.

The indications of direction used in the description and in the claims,such as “up”, “down”, “left”, “right”, “upper”, “lower”, and otherdirections or orientations are mentioned in order to afford greaterclarity with reference to the figures. These indications are notintended to limit the scope of the invention.

In the present document, the verbs “have”, “comprise”, “include” orequivalent are used in a broad sense, generally signifying “includingbut not limited to”.

The word “or” is generally employed in a broad sense covering “and/or”unless the context clearly indicates the contrary.

In the present invention, a channel can be defined as being a flowconduit of hollow and elongate shape allowing the passage of a liquidand/or of a gas from one location to another. It can take the form of aflexible tube or tubing or of a cavity inside a cassette. Some channelshave valves that can be actuated preferably by means of a linearactuator governed by a controller in order to close or open the channel.Without actuation, said valves are preferably closed. A chamber can be acavity or a channel having several inlets and/or outlets or can take theform of a simple intersection of two channels. Each chamber has an inletcalled inlet channel and an outlet called outlet channel.

Principle of the Invention Concerning a Blood Treatment System

The embodiment shown schematically in FIG. 27 is a simplifiedembodiment. The treatment system comprises three pumps (507, 508, 509),three flow paths and a filtration means or filter (513). The first flowpath starts from the filtering means (513) and reaches to the reservoir(517), also called the fluid recovery means. The fluid flowing throughthe first flow path is called the filtrate. The second flow path startsfrom the patient, passes through the filter (513) and returns to thepatient (500). The fluid flowing through the second flow path is theblood of the patient. The third flow path is supplied with a fluidgenerally called dialysate (although the invention is not limited tothis fluid) which flows from the first liquid supply means, likewisecalled dialysate reservoir (514). The dialysate initially flows throughthe third flow path, after which it flows into one or more secondaryflow paths (in diluted form or transformed). The dialysate (or otherfluid of the third flow path) can:

-   mix with the blood:    -   before the filter (513) in order to effect a pre-dilution,        and/or    -   after the filter (513) in order to effect a post-dilution,        and/or    -   supply the filter (513).

In order to permit these different solutions and thereby perform anytreatment technique by dialysis, the system requires three chambers(501, 502, 503). The second chamber (502), also called distributionchamber, makes it possible to direct the dialysate toward the filter(513), the first chamber (501) in order to effect a pre-dilution and/orthe second chamber (502) to effect a post-dilution. The first and thirdchambers (501, 503) can also be called connection chamber. The first andthird chambers (501, 503) make it possible to mix the blood with thedialysate, in other words the first and third chambers (501, 503) allowthe fluid of the third flow path to flow into the second flow path. Thechannels connecting the chambers to each other or to the filter cancomprise valves (519) and/or a flow-restricting or closure means (520).

FIG. 28 schematically depicts a more complex system with the addition offurther optional elements. These can be, for example:

-   A new supply system (515) that can contain, for example, an    anticoagulant. This fluid can be contained in a reservoir (515) and    delivered by a pump (510) or by gravity. This supply means can be a    syringe and/or-   Another supply means (516) that can contain, for example, an agent    inhibiting the anticoagulant. This fluid can be contained in a    reservoir (516) and delivered by a pump (512) or by gravity. This    supply means can be a syringe, and/or-   A new channel for connecting the third chamber (503) (that normally    used for the post-dilution), or another chamber (located downstream    of the third chamber), to the first chamber (501) (that normally    used for the pre-dilution), or to another chamber (504) (located    upstream of the first chamber), this new channel preferably    comprising a valve controlled by a controller. It allows the fluid    contained in the second flow path to circulate in a loop so as not    to stagnate in the channels, and/or-   Another channel for connecting the third chamber (503) to the fluid    recovery means (517). This channel preferably comprises a valve. It    can permit, for example, the priming of the system or the disposal    of some of the fluid flowing in the second flow path, and/or-   A heating means (522)

Another embodiment is disclosed by FIG. 29. This embodiment can compriseat least one pressure sensor (518), located in or near the chambers(504, 501, 502, 503), the filter (513) and/or the supply means (515,516, 514), and/or an additional pump (511) (in place of the flow limiter(520)) in the third flow path between the distribution chamber (502) andthe connection chamber (501). The system can additionally comprise acalibration system that can comprise a sensor common to the first andthird flow paths. This calibration system comprises two supplementarychannels that allow the fluids contained in the first and third flowpaths to flow toward a sixth chamber (506). This sixth chamber (506)comprises or has connected to it a sensor permitting the calibration ofelements (sensors and/or pump) of the first and third chambers such thatit is calibrated identically.

FIG. 30 discloses a treatment system as described above. This systemadditionally comprises a cassette (601) permitting the functions ofdistribution of fluids. This cassette (601) is connected to reservoirs(603, 604) and cooperates with a device (602). The device (602), calleddialysis apparatus, can be reusable, while the cassette (601) can bedisposable. The device (602) can comprise a processor (605), at leastone sensor (606) designed to cooperate with the cassette (601), at leastone actuator (607) (for example pump or control means) designed tocooperate with the cassette (601), a screen (608), at least oneacquisition means and/or other, such as a battery (609) and/or a memory(610).

Embodiments of Cassettes According to the Operating Principle DescribedAbove

According to FIG. 1, the invention discloses a system (14) with which itis possible to carry out treatment of a patient's blood and whichcomprises a blood filtration means (3), at least one liquid supply means(F1), two patient tubes, namely an outlet tube (5) for collecting theblood to be treated and an inlet tube (6) for re-injecting the treatedblood into said patient, a filtrate recovery means (F4), at least threefluid pumps (P1, P2, P3), a cassette (2, 2′) composed of channels andvalves for directing the fluids. Said cassette (2, 2′) comprises atleast one distribution chamber (C1, C1.2, C7) comprising a single inletchannel and at least two outlet channels. Said treatment system (14)comprises a controller for controlling the opening and closure of saidvalves depending on the desired treatment.

Said treatment system (14) additionally comprises a first flow pathconnecting said blood filtration means (3) to the filtrate recoverymeans (F4), composed of a series of channels and a dedicated pump (P3);a second flow path dedicated to the circulation of the blood, comprisinga series of channels, said blood filtration means (3), said patienttubes (5, 6) and a dedicated pump (P1); a third flow path composed of aliquid supply means (F1), at least one dedicated pump (P2), a series ofchannels, a heating means (4) and at least one distribution chamber (C1,C1.2).

Advantageously, said distribution chamber (C1) comprises at least three(separate) outlet channels connected directly or indirectly

-   -   to the second flow path upstream of said blood filtration means        (3),    -   to the second flow path downstream of said blood filtration mans        (3),    -   to said blood filtration means (3).

Said cassette can additionally comprise a flow regulator designed togovern the amount of liquid of the third flow path flowing into at leastone of said outlet channels of said distribution chamber (C1). Moreover,said at least one flow regulator is controlled by said controller, whichcan comprise the processor (605).

Said cassette (2′) can likewise contain the pumps and/or other elements.

The treatment system additionally comprises, in the third flow path, aflow adjuster (13, P2′) located between said distribution chamber (C1)and said first connection chamber (C2).

In one embodiment, the third flow path has an additional pump (P2′) inthe third flow path, located between the distribution chamber (C1) andsaid first connection chamber (C2). Said additional pump (P2′) has thecomplete or partial role of flow adjuster. The aim of the flow adjusteris to control the flow of the fluid passing from the distributionchamber (C1) to the connection chamber (C2). The adjuster thus makes itpossible to distribute the quantity of fluid in the connection chamber(C2) and at least one other connection chamber or the blood filtrationmeans (3).

In one embodiment, one or more flow adjusters (also called flowrestrictors) can be placed between any chamber or element (for exampleblood filtration means (3)). A flow adjuster (13) can be a pump, aproportional valve and/or a set of channels with dedicated valve anddifferent diameters, etc. A supplementary safety valve can be addedupstream or downstream of the flow adjuster (13-520). A flow adjusterpermits a 0% to 100% flow of the fluid, at one moment or during a givenperiod, through said flow means. In other words, the flow of a fluidcoming from at least one liquid supply means can be distributed betweenthe different channels according to the requirements of the treatment.

In one embodiment, the treatment system (14) comprises a second liquidsupply means (F2-515) located on the patient outlet tube (5) or in thecassette (2, 2′-601). Said second supply means can contain ananticoagulant such as citrate, heparin, danaparoid sodium or similar.

In one embodiment, said system (14) comprises a third liquid supplymeans (F3-516) located on the patient inlet tube (6) or in the cassette(2, 2′-601). Said liquid supply means can contain calcium or an agentinhibiting the anticoagulant.

On the patient inlet tube (6) and/or in the cassette (2, 2′-601), thesystem comprises at least one safety element (7) for detecting airbubbles in the second flow path and/or for stopping the circulation ofthe blood and/or a means for capturing said air bubbles.

Location of the Heating Means and/or use of Two Pumps in the Third FlowPath:

According to the operating principle disclosed by FIG. 31, in order tobe effective, the fluid distribution system (whether for a cassette asdescribed in the present document or for another distribution system)can comprise a precision pump (702), a fluid supply means, a flexiblebag (703) and an additional distribution pump (707). The systemadditionally comprises a main flow path (701) which divides into atleast two secondary and separate flow paths (704, 704′). The precisionpump (702) and the flexible bag (703) are positioned in the main flowpath (701), the flexible bag being positioned downstream of said pump.Thus, all the pumped fluid is known with precision and can at least inpart be stored at least temporarily in the flexible bag. The additionalpump (707) is positioned in one of the secondary flow paths (704).Preferably, the other secondary flow path (704′) comprises a valve(705). In one embodiment, at least one flow path comprises a pressuresensor (706) positioned downstream of the precision pump (702).Preferably, said pressure sensor (706) is positioned in the secondaryflow path (704), which comprises the additional pump (707), and upstreamof the additional pump. The flexible bag (703) is preferably a heatingmeans.

Given that some techniques of continuous renal replacement therapyrequire heating the dialysate and/or substitution liquid during itsinjection, said heating means (4) can be located at various locations ofthe third flow path. In one embodiment, the cassette has a heating means(4) inside the distribution chamber (C1) or upstream of the latter.

In one embodiment according to the principle described above, theheating means (4) is a flexible bag located between the main pump (P2)of said third flow path and said distribution chamber (C1), which makesit possible to create a constant positive pressure in said bag (4). Theheating means is supplied continuously by the pump (P2), which makes itpossible, among other things, to guarantee proper control of thereheating of the liquid of the third flow path. Said bag (4) is thendirectly connected to the inlet channel (V9) of the distribution chamber(C1).

As a result of this configuration, all the injected liquid passesthrough a single pump (P2). The pre-dilution pump (P2′) (also calledadditional pump) only distributes the liquid before and/or after thefilter. Thus, a single precision pump is necessary. The pump (P2) is theprecision pump and allows the quantity of pumped fluid to be known. Theadditional pump simply permits distribution between the pre-dilution(before the filter) and the post-dilution (after the filter). The use ofthe pumps is as follows:

-   -   If only post-dilution is programmed: the pre-dilution pump (P2′)        is stopped and all the liquid will be injected after the filter        (3). The post-dilution valve (V8) is opened. The pre-dilution        valve (V5) is preferably closed.    -   If only pre-dilution is programmed: the post-dilution pump (P2)        delivers the substitution volume. The post-dilution valve (V8)        prevents passage of the liquid after the filter. The        pre-dilution pump (P2′) also makes it possible to regulate the        fluid so as to avoid the pressure in the heating means (4)        becoming negative.    -   If pre-dilution and post-dilution are programmed: the main pump        (P2) delivers all the substitution volume required (pre and        post). The post-dilution valve (V8) is opened. The pre-dilution        pump (P2′) taps some of the liquid in order to inject it before        the filter (3). If there is an error of precision in the        distribution before and after injection, its seriousness is        limited because the volume is in any case injected into the        patient.

Use of the Cassette Depending on the Various Treatments:

-   Slow continuous ultrafiltration (SCUF): FIG. 2 shows the use of the    cassette applying a treatment of slow continuous ultrafiltration.    This technique is used to eliminate excess liquid by means of the    convection principle.

Thus, the controller opens only the valve V1 of the second flow path andcloses the valves V5, V7 and V8 of the third flow path. The pumps P1 andP3 then function, while P2 and P2′ do not function.

-   Continuous venovenous hemofiltration (CVVH): FIG. 3 shows the use of    the cassette applying a treatment of continuous venovenous    hemofiltration. This technique is used to obtain the removal of    dissolved substances by means of the convection principle. A    substitution solution is injected into the circuit before    (pre-dilution) and/or after (post-dilution) the filtration means    (3).

Thus, the controller opens the valves V1 of the second flow path and V5and/or V8 of the third flow path, and the valve V7 is closed. The pumpsP1, P2 (optionally P2′) and P3 function.

-   Continuous venovenous hemodialysis (CVVHD): FIG. 4 shows the use of    the cassette applying a continuous venovenous hemodialysis    treatment. This technique is used to obtain the removal of dissolved    substances (small molecules: urea, creatinine, K, etc.) and to    obtain a water equilibrium by the diffusion principle. The dialysate    is injected into the filtration means (3).

Thus, the controller opens the valves V1 of the second flow path and V7of the third flow path, and the valves V5 and V8 remain closed. Thepumps P1, P2 and P3 function.

-   Continuous venovenous hemodiafiltration (CVVHDF): FIG. 5 shows the    use of the cassette applying a treatment of continuous venovenous    hemodiafiltration. This technique is used to obtain the removal of    dissolved substances (small or medium-sized molecules) by means of    the principles of diffusion and convection. The dialysate and/or a    substitution solution are injected into the filtration means (3) and    into the blood after the filtration means (3).

Thus, the controller opens the valve V1 of the second flow path and alsothe valves V7 and V8 of the third flow path. The valve V5 remainsclosed. The pumps P1, P2 and P3 function. In this embodiment, the outletchannels V7 and V8 are proportional valves or another means ofcontrolling the flow that passes through these valves.

In another embodiment, shown in FIG. 5′, the cassette comprises asupplementary distribution chamber (C1.2) and a supplementary connectionchamber (C1.1). Said supplementary distribution chamber (C1.2) issupplied directly by the additional pump (P2′). Said supplementarydistribution chamber (C1.2) makes it possible to distribute thedialysate or substitution product either to the first connection chamber(C2) for the pre-dilution or to said supplementary connection chamber(C1.1). Said supplementary connection chamber (C1.1) is also suppliedwith dialysate or substitution product by the first distribution chamber(C1) by means of the outlet channel with dedicated valve (V7′). Saidsupplementary connection chamber (C1.1) also has an outlet channel (V7″)connecting to the filter (3). The benefit of such an arrangement is toincrease the precision of the quantities injected into the filter andinto the second connection chamber for the post-dilution or into thefilter and into the first connection chamber for the pre-dilution. Thus,the additional pump (P2′) ensures that the quantities of fluid that areto be distributed are distributed with precision. In this embodiment,for a continuous venovenous hemodiafiltration treatment, the valves V1,V8 and V7″ are opened.

-   Therapeutic plasma exchange (TPE): FIG. 6 shows the use of the    cassette applying a therapeutic plasma exchange. This technique    permits plasma exchange by membrane filtration. A substitution    solution is injected in order to replace the extracted plasma.

Thus, the controller opens the valve V1 of the second flow path and alsothe valve V8 of the third flow path. The valves V5 and V7 remain closed.The pumps P1, P2 and P3 function. Preferably, F2 and F3 deliver theirfluid in the second flow path.

-   Hemoperfusion: FIG. 7 shows the use of the cassette applying a    treatment of hemoperfusion. This technique is used to eliminate the    toxic substances from the blood of a patient, where the filtration    means contains an absorbent substance. A substitution solution is    injected in order to replace the extracted plasma.

Thus, the controller opens the valve V1 of the second flow path and alsothe valve V8 of the third flow path. The valves V5 and V7 remain closed.The pumps P1 and P2 function, while the pump P3 does not function.Preferably, F2 and F3 deliver their fluid in the second flow path.

System having Several Liquid Supply Means

When one flow path (coming, for example, from a supplementary liquidsupply means) connects to another flow path, the cassette preferablycomprises a connection chamber permitting the intersection of said twoflow paths.

In an embodiment shown in FIG. 8, the cassette comprises:

-   A third connection chamber (C4) comprising an inlet channel (V1′),    an inlet channel with dedicated valve (V1) and an outlet channel    (V2). This connection chamber introduces a fluid, contained in a    second liquid supply means (F2), into the flow path of the blood    (second flow path), and said second liquid supply means (F2)    preferably contains an anticoagulant agent, and/or-   A third inlet channel (V12′) in the second connection chamber (C3).    The third inlet channel (V12′) allows a fluid, contained in a third    liquid supply means (F3), to be injected into the flow path of the    blood (second flow path), and said third liquid supply means (F3)    preferably contains an agent inhibiting the anticoagulant, and/or-   A fourth connection chamber (C5) comprising at least two inlet    channels (V14, V14′) with dedicated valve, making it possible to    have at least two different or similar fluids in the third flow    path, for example dialysate in one bag and a substitution product in    another.

Circulation without Interruption, Emptying and Priming of the Secondand/or Third Flow Path:

In an embodiment shown in FIG. 9, the second connection chamber (C3)comprises:

-   -   An inlet channel (V11) of the second flow path connected to the        filtration means (3)    -   An inlet channel (V12) of the third flow path connected to the        distribution chamber (C1)    -   Three outlet channels with dedicated valve (V10, V10′, V10″),        the first being connected to the patient inlet tube (6), the        second being connected to an inlet channel of the second        connection chamber (C4), and the third being connected either to        a recovery means (F5) or directly or indirectly to the filtrate        recovery means (C6).

This embodiment permits the following, for example:

-   If a problem occurs, the controller can close the valve V10 in    order, for example, to avoid injecting an air bubble into the    patient, or another element that may endanger the patient's life. In    this case, the blood remaining in the cassette and the filter risks    coagulating. It is therefore imperative that the blood does not    stagnate in the cassette or in the filter. Thus, P1 continues to    function, collecting blood from the second connection chamber in    order to circulate blood in a loop between the first and second    connection chambers and the filter. V10′ and/or V1″ are opened,    while V1, V10 and V10″ are closed.-   to take samples of the blood by virtue of the valve V10″,-   to start the treatment by emptying the air from the system,-   to rinse the second flow path with the fluid from the third flow    path,-   to eliminate all or some of the fluid contained in the second and/or    third flow path.

Means and Method for Calibration of the Pumps and/or Sensors of theFirst and Third Flow Paths:

Some techniques of continuous renal replacement therapy require preciseknowledge of the quantity of the volume injected and withdrawn via thethird flow path and first flow path, respectively. The treatment systempreferably comprises peristaltic pumps. This type of pump may have acertain imprecision. Thus, according to FIG. 10, in order to know withprecision the volume quantity added or withdrawn, the distributionsystem comprises at least two volume sensors, which are able to measurethe volumes of the third and first flow paths.

The first sensor (15) is arranged in the third flow path between thedistribution chamber (C1) and the main pump (P2) and measures theinjected volume coming from the first liquid supply means (F1, F1′).Preferably, the sensor (15) is located after the heating means (4). Thesecond sensor (17) is placed in the first flow path downstream of thepump and before any other chamber. Said second sensor (17) measures thevolume of the filtrate withdrawn. To avoid any risk of contamination,the two sensors are preferably located in the cassette. In a preferredembodiment, the treatment system comprises:

-   -   a third volume sensor (16) for comparing the volumes measured by        the two preceding volume sensors (15, 17), said sensor also        being called a reference sensor,    -   a means of sampling the fluids coming from the first and third        flow paths. Said sampling means comprises a sixth connection        chamber (C8) having an outlet channel directly connected to said        third sensor (16) and two inlet channels (V19, V20) connected        respectively to:    -   an outlet channel with dedicated valve (V21) located in the        first distribution chamber,    -   an outlet channel with dedicated valve (V15) located in the        second distribution chamber,    -   optionally, a seventh connection chamber (C9) allowing the        reference sensors (16) to discard the liquids measured in the        filtrate recovery means (F4).

To avoid any risk of contamination, said third sensor can preferably belocated in the cassette.

The method comprises the following steps:

-   -   calibration of the volume injected:    -   opening of the valve (V21) and closure of the other valves,    -   actuation of the main pump (P2) of the third flow path,    -   measurement of the volume pumped by said pump

(P2) via said first sensor (15) of said third flow path,

-   -   measurement of said pumped volume via the reference sensor (16),    -   comparison of the two measurements,    -   calibration of the first sensor (15) and/or of the pump (P2)    -   calibration of the volume withdrawn:    -   opening of the valve (V15) and closure of the other valves,    -   actuation of the pump (P3) of the filtrate of the first flow        path,    -   measurement of the volume pumped by said pump (P3) via said        second sensor (17) of said first flow path,    -   measurement of said pumped volume via the reference sensor (16),    -   comparison of the two measurements,    -   calibration of the first sensor (15) and/or of the pump (P2).

These steps can be performed at the time of priming and/or during thetreatment.

The first and second sensors (15, 17) are set to a common sensor calledreference sensor (16) for relative optimum precision. Said sensors,although inexact, are sufficiently effective, since they are(relatively) exact in comparison with the reference sensor (16).

Said reference sensor (16) can be a balance, a volumetric pump, a massflow sensor or any sensor by which a volume can be measured or deduced.

Preferably, said first and second sensors (15, 17) continuously measurethe liquids passing through the third and first flow paths,respectively. By means of the continuous measurement of the volumes, itis possible to compensate for possible drifting.

Pressure Sensor Offset from the Flow Path:

According to FIGS. 11, 12 and 13, the present invention discloses afluid distribution system (100) (preferably a cassette as describedabove) by means of which it is possible to sample and/or deliver a fluidF11 from and/or to the patient and to measure the pressure of said fluidF11. The system comprises a rigid body (105) composed of at least oneflow path (103), through which said fluid F11 flows, and at least onechannel (102). Said channel (102) is separate from the flow path (103)and makes it possible to connect said flow path to a measuring zone(101). The system additionally comprises at least one opening (106)covered by a flexible membrane (104) forming said measuring zone. Themembrane is designed to receive a pressure sensor (107).

A fluid F12 different than the fluid F11 is contained in said measuringzone (101). The fluid F12 extends at least in part into said channel(102). Said fluid F12 makes it possible to transmit the pressure of thefluid F11 to said membrane (104) by contact. Said channel (102) is aflow restrictor designed in such a way that said fluid F11 cannot comeinto contact with said membrane. The length and/or the shape of saidpressure transmission channel (102) depends on the expansion capacity ofsaid fluid F12 and/or on the range of pressure to be measured.Preferably, the channel (102) comprises at least one section that issufficiently narrow to retain the fluid F11 so that said fluid does notenter said measuring zone (101).

In one embodiment, the channel (102) comprises a hydrophobic filter(108) or a membrane.

In one embodiment, an interface of membrane (104)/fluid (F13)/cell ofthe sensor (107) is created so as to avoid friction by the membrane(104) on said cell, which could create disturbances in the measurement.An interface of liquid (F11)/fluid (F12)/membrane (104) is created inorder to avoid the membrane (104) being wetted by the liquid (F11). Thetransmission of the pressures of F11 is ensured by the fluids F12 andF13 arranged on each side of the membrane (104). F12 and F13 preferablyhave the same physical properties. Preferably, F12 and F13 are air. Saidmembrane (104) can deform with equivalent stresses on each side of thesefaces, so as to compensate for the variations in the volume of air,trapped between the membrane (104) and the sensor (107), due to thetemperature.

In another embodiment, the fluid F11 is aqueous, while F12 is lipid, andF13 can be either lipid or aqueous.

In another embodiment, FIG. 13′ discloses a fluid distribution system(100) which permits the flow of a fluid F11 and makes it possible tomeasure the pressure of said fluid F11. The system comprises a rigidbody (105) composed of at least one flow path (103), through which saidfluid F11 flows, and at least one channel (102). Said channel (102) isseparate from the flow path (103) but communicates so that the fluid F11can flow in the channel (102). Thus, the channel (102) makes it possibleto connect said flow path to a measuring zone (101). The systemadditionally comprises at least one opening (106) covered by a flexiblemembrane (104) forming said measuring zone. Said opening (106) can be ofa size equal to or different than the size of the channel (102). Inaddition, the membrane is designed to receive a pressure sensor (107). Afluid F12 different than the fluid F11 is contained in said measuringzone (101). The fluid F12 is contained at least in part in the measuringzone and/or in the channel (102).

In an embodiment again illustrated by FIG. 13′, the quantity and/or thevolume of the fluid F12 is constant or can decrease over the course oftime such that the fluid F11 advances with greater or lesser speed inthe channel (102) and/or the measuring zone (101).

In one embodiment, the measuring zone (101) and/or the channel (102)contain at least in part the fluid F12 and the fluid F11. The fluid F11can partially wet or be in contact with the membrane (104). The lengthand/or the shape of said pressure transmission channel (102) depends onthe expansion capacity of said fluid F12 and/or on the range of pressureto be measured.

The channel (102) can be designed in such a way as to limit and/or slowthe progress of the fluid F11, for example, during the use of saidsystem. The fluid distribution system (100) can be adapted in such a wayas to guarantee that the membrane (104) and/or the measuring zone (101)are not completely wetted by or in contact with the fluid F11 during theuse of said system.

Energy-Saving Linear Actuator:

The invention discloses a linear actuator (200) using a motor (forexample a direct-current motor (or DC motor) or another type of motorknown to a person skilled in the art) (201) coupled to interposed meansthat make it possible to transform the rotation of the motor shaft intoa linear movement. Preferably, the motor can also comprise a torquereducer.

In particular, the interposed means comprise:

-   -   at least one peripheral ramp (214) arranged inside a piston        (207),    -   at least one bearing means (209) fixed directly or indirectly to        the rotor (208) of said electric motor (201), said bearing means        (209) being designed in such a way as to cooperate with said        peripheral ramp (214),    -   at least one guide means (203, 216) allowing the piston (207) to        guide the translation movement.

Said ramp (214) comprises at least one threshold, of which one threshold(215) is located at the summit of said ramp (214). In one embodiment, atleast one threshold can be designed in such a way as to cooperate withthe bearing means. For example, the threshold can be perfectly flat andhorizontal with respect to the vertical movement of the piston. Thethreshold can also have a specific shape for ensuring a good hold of thebearing means in order to guarantee that the position is maintained, forexample the embodiment on the right in FIG. 18′. In addition, thethreshold (215) located at the summit of said ramp (214) can be followedby a passage (219) allowing the piston (207) to free itself of thestresses exerted by said bearing means (209).

The piston can comprise one or more ramps and/or one or more passages.At least one ramp can have an inclination of between 0 and 90°. In oneembodiment, said inclination can be between 0 and 45°, preferablybetween 10 and 30°.

Said piston (207) comprises at least two stationary positions:

-   a first position, in which the piston (207) is situated at a    distance (d2) equal to A. In this position, the bearing means (209)    is located at the start of the ramp;-   a second position, in which the piston (207) is situated at a    distance (d2) equal to B. In this position, the bearing means (209)    cooperates with a threshold allowing the piston to maintain this    position.

The system has several advantages:

-   -   No need to power the motor in order to keep the valve opened        (3rd stable state).    -   The actuator will not heat when maintaining a position.    -   Low operating noise.    -   Substantial travel.

In a preferred embodiment such as is shown in FIG. 16, the piston (207)has at least one ramp (214) (preferably two or more) and the bearingmeans can be a transverse shaft adapted to cooperate at leasttemporarily with said at least one ramp. Thus, when the piston comprisestwo ramps positioned symmetrically with respect to the center of theshaft of the rotor, for one complete turn of the rotor, the piston canon two occasions be at the second position and first position. Thepiston can comprise a passage (219) permitting a rapid transition fromthe second position to the first position, and said passage can extendbelow the first position. This makes it possible:

-   -   to obtain two positions of the piston (first and third        positions) without actuation of the actuator,    -   to make assembly easier,    -   to prevent the rotor (or the motor) from turning when the piston        is in the third position, which makes impossible any change of        position when the cassette is not loaded in the apparatus.

According to one embodiment, the ramp is followed by at least onepassage, preferably after a threshold.

In one embodiment, said actuator additionally comprises at least onecompression means (205) exerting a force against the piston (207). Thebearing means and the ramp cooperate in order to move the piston on thesame axis as the force exerted by the compression means, but in anopposite direction.

In one embodiment, said compression means tends to push the piston back(with respect to the actuator) (that is to say in the direction (220) ofthe distal end of the piston (217)) while the bearing means and the rampcompel the piston to move toward the actuator. In this case, A>B. Inanother embodiment, said compression means tends to move the pistontoward the actuator while the bearing means and the ramp compel thepiston to move away from the actuator. In this case, A<B.

In one embodiment, the aim of the actuator is to drive an element of anapparatus such as that described in the present document. This can be,for example, a valve of the cassette. The rest of the descriptiondescribes this embodiment, but it goes without saying that the inventionis not limited to this embodiment.

Thus, said piston (207) comprises at least two positions:

-   a first position, in which the stub (211) of the piston (207) is    coupled to the valve (212) (illustration in FIG. 15) of a cassette    such as that described above. The piston (207), not constrained by    the bearing means (209), maintains the valve (212) in a closed    position against the seat of the valve (213). Here, d2 is equal to    A.-   a second position, in which the stub (211) of the piston (207) is    coupled to the valve (212). The piston (207) is constrained by the    bearing means (209), moving the piston/stub assembly in the    direction (221) of the motor (201). When said bearing means (209)    arrives at the threshold (215) situated at the summit of the ramp,    the piston (207) is in the second position and the valve (212) is in    the opened position. Here, d2 is equal to B.

In one embodiment, the piston has a third position, in which the stub(211) of the piston (207) is decoupled from the valve (212). Acompression means (205) exerts a force against the piston, moving saidpiston toward a third position farther from the motor than the first andsecond positions. This can be the same compression means as describedabove or a separate compression means. Here, d2 is equal to C. In thisembodiment, C>A>B. The benefit of this third position is to guarantee asufficient occlusion pressure when the piston is coupled to the valve inthe first position. In other words, when the piston is coupled to thevalve, the piston exerts a force against the valve in order to ensurethe closure of the valve when the piston is in the first position.

In one embodiment, the actuator comprises an element for fixing to itssupport, comprising a compression means exerting a force in thedirection of the distal end of the piston and having the same functionas described above.

Said compression means (205) can be a spring, an elastic blade, anelastic material or a shape-memory material. Said compression means(205) can exert a force of 0 to 6 N, preferably of between 5 and 6 N.

The actuator (200) is designed with the aim of not consuming energywhile a stationary position is maintained. The bearing means (209) isdesigned to slide or roll on the ramp in order to reach a position. Whenthe bearing means (209) stops on a threshold, said threshold is designedin such a way that the assembly is at equilibrium. The threshold (215)at the summit of the ramp (214) is directly followed by a passage (219)allowing the piston to pass rapidly from a second position to a firstposition while consuming a minimum amount of energy. Said passage makesit possible to pass from one position to the other with a small amountof energy. In other words, the energy consumed by the actuator forpassing from the first position to the second position is greater thanthe energy consumed by the actuator for passing from the second positionto the first position. The passage (219) can be a ramp having a highslope and/or oppositely directed to the slope of the ramp. Thus, thebearing means travels a shorter distance to pass from the secondposition to the first position than the other way round.

Optionally, the piston (207) comprises several thresholds in order tohave intermediate rest positions.

In one embodiment, the motor comprises a torque reducer between themotor and the rotor of the interposed means. Said torque reducer can bedesigned in such a way that the motor can turn the rotor but the rotorcannot turn the motor. In other words, the torque reducer, by virtue ofits design, can prevent or limit or brake any movement of the rotor thatis not due to the motor.

In one embodiment, the torque reducer can be designed in such a way thatthe actuator can maintain any position when the motor is stationary(powered or not). Thus, the actuator can comprise a limited number ofthresholds as described above, but an unlimited number of positions thatcan be maintained by virtue of the torque reducer without the actuatorbeing fed with current. Such an actuator can be adapted to cooperatewith a proportional valve of a fluid distribution cassette. Thus, bymeans of this design, the actuator can permit the flow of a fluidproportionally to the requirement of the treatment.

In one embodiment, the piston (207) does not comprise any threshold butonly positions that can be maintained by virtue of the torque reducer asdescribed above. This piston thus comprises at least one ramp andoptionally one passage. The torque reducer allows the actuator tomaintain a given position permitting the 0% to 100% opening of a valve(for example a proportional valve).

In one embodiment, the piston comprises at least one lower ramp andupper ramp, said ramps being adapted such that at least one bearingmeans (209) can move between said ramps. Said ramps can at least in partbe parallel with respect to each other.

In a preferred embodiment, at least one actuator is arranged in anactuation system which comprises a controller and at least one powersupply means. Said system is designed to move at least one piston from asecond position to a first position and vice versa while consuming asmall amount of energy. Said power supply means can be an external powersupply and/or an energy storage means. Said energy storage means can beused by the system when said external power supply is no longeroperative or is inadequate. Thus, in the event of an outage, the valvewill move from the open to the closed state by virtue of the use of saidenergy storage means, which can be a supercapacitor, or a battery.

According to an embodiment disclosed by FIG. 14, the actuator (200) canbe composed of:

-   -   a motor (201),    -   a rigid envelope (202) inside which are arranged:        -   a sensor (204) fixed to the motor with said envelope (202),        -   a compression means (205),        -   a piston (207) in which is fixed an element (206) designed            to cooperate with said sensor (204),        -   a bearing means (209) fixed directly or indirectly to the            rotor (208) of the motor (201),        -   an element (210) fixed to the distal end (217) of the piston            permits fixation of a stub (211) which will be coupled to a            valve.

The piston (207) and the rigid envelope (202) comprise guide means (203,216) to avoid the piston turning with the rotor (208) of the motor.

FIGS. 17, 18, 19, 20 and 21 show the piston in different positions (thevalve and the stub are not shown in these figures):

-   -   FIG. 17: The valve is not coupled to the stub. The piston (207)        is in the third position with the compression means (205)        relaxed. The bearing means (209) is in the passage (219) and        does not exert any force against the ramp (214).    -   FIG. 18: The valve is coupled to the stub. The piston (207) is        in the first position, and the compression means (205) exerts a        pressure against the piston (207) in order to guarantee the        closed position of the valve. Preferably, the bearing means        (209) and the ramp (214) do not exert any stress. FIG. 18′        reveals two different embodiments of the threshold (215) at the        summit of the ramp. Thus, according to one embodiment, said        threshold can have a different shape, it can be flat or designed        more or less for greater cooperation with the bearing means        (209) when the latter is situated near and/or on the threshold        (215).    -   FIG. 19: The valve is coupled to the stub. The rotor (208) is in        motion in order to allow the piston (207) to pass from the first        position to the second position. The bearing means (209) travels        on the ramp (214) and compels the piston (207) to move toward        the motor (opening of the valve) and compresses the compression        means (205).    -   FIG. 20: The valve is coupled to the stub. The piston (207) is        in the second position, and the bearing means (209) stops on the        threshold (215) at the summit of the ramp. The compression means        (205) is compressed. The valve is opened. The position is stable        without contribution from the motor (201). In one embodiment,        the actuator comprises a sensor designed to establish the        relative position of the piston (207). The embodiment shown in        FIG. 20 reveals a Hall effect sensor (204) cooperating with a        magnet (206) housed in the piston. The sensor (204) can be a        linear displacement sensor comprising a rod or an encoder or any        elements (206) suitable for cooperating with said sensor (204).        In addition, by virtue of the processor connected to the sensor        (204), it is possible to establish or monitor the position of        said piston (207).    -   FIG. 21: The valve is coupled to the stub. The rotor (208) is in        motion, causing the bearing means (209) to move in the passage        (219). The piston moves instantaneously from the second position        to the first position by virtue of the compression means (205)        which pushes the piston (207) back in the direction of the        distal end of the piston (217). The valve closes.

Control System, and Control of an Actuator

In an embodiment disclosed by FIGS. 32, 32′ and 33, a control system(800) comprises a linear actuator comprising a movable part (801) and astationary part (804) and also control elements (802, 803, 805). Thecontrol elements are adapted to establish the position of the movablepart (801) with respect to the stationary part (804) and to control thelinear actuator.

FIG. 32 shows the actuator in a position A, and FIG. 32′ shows theactuator in a position B. The control element (805) controls theactuator, of which the stationary part (804) can comprise the drivemeans (for example a motor). The movable part (801) can be adapted tocooperate with, for example, a valve of a fluid distribution system.Thus, the position A could correspond to the closed position of thecontrolled valve, and the position B could correspond to the openedposition of said valve. However, the invention is not limited tocontrolling the opening and closing of a valve of a fluid distributionsystem, and the number of positions can be limited or unlimited.

The elements 1 (802) and 2 (803) of the sensor are designed to cooperateand determine at least one position. This can entail a capacitive orinductive displacement sensor (LVDT, etc.), an electromagnetic sensor(Hall effect sensor), ultrasonic sensor, infrared sensor, opticalsensor, laser-type sensor, mechanical sensor or microwave sensor (listnot exhaustive). In our example, and to aid understanding, we will use aHall effect sensor. Thus, the element 1 (802) is a permanent magnet (inthis case it is not connected to the processor) (805), and the element 2(803) is a Hall effect sensor connected to the processor. The permanentmagnet creates an electromagnetic field, of which the sensor (803)measures the strength. In particular, the sensor (803) makes it possibleto detect the variation of the magnetic field induced by the permanentmagnet (802) when the latter moves.

Preferably, the permanent magnet (802) is rigidly fixed in a definitivemanner to the movable part (801) of the actuator, and the sensor (803)is rigidly fixed in a definitive manner to the stationary part (804) ofthe actuator (or the other way round). Thus, when the movable partmoves, the permanent magnet (802) moves toward or away from the sensor(803), which thus measures a variation in the strength of the magneticfield of the permanent magnet (802). Ideally, the magnet and the sensorare aligned.

The measurement data of the sensor (802) are transmitted to theprocessor in order to process the signal. Normally, all the controlsystems have to be graded in order to determine in advance the strengthcorresponding to each position. In other words, the sensor generallydetects predetermined threshold values corresponding to respectivepositions determined in advance. However, this grading work (for examplecalibration to be carried out on all the actuators) is lengthy andlaborious. To avoid this grading work, the invention discloses the useof a processor that processes the signal in order to determine at leastone position of the actuator. Thus, the invention makes it possible toavoid performing a calibration.

The upper graph in FIG. 33 reveals that the absolute value (strength ofthe electromagnetic field of the magnet measured by the sensor) can bevery different from one actuator to another. This is because the sensorsof the actuators 1 and 2 do not show the same strength (in absolutevalue) although their position is identical. Thus, it would be difficultand unreliable, or even impossible, to determine the position of theseactuators as a function of a single threshold value.

The control system (800) comprises a processor (805) which uses amathematical model taking account of the derivative of the absolutevalue. In the present document, the absolute value is the value measuredby the sensor (803) and corresponds to the strength of the magneticfield. The curve of the absolute value is shown by the upper graph inFIG. 33. The derivative of the absolute value is the directorcoefficient of the curve plotted by the absolute value. In other words,the derivative makes it possible to establish the slope of the variationof the magnetic field when the magnet moves with respect to the sensor.This derivative is shown by the curve in the middle graph of FIG. 33.Thus, this derivative makes it possible to establish the direction ofdisplacement of the movable part (801) of the actuator with respect toits stationary part (804).

The control system thus comprises a processor using a mathematical modelthat takes account of the derivative of the signal. By virtue of thismathematical model, it is possible to know when the actuator has reacheda position or a threshold of the kind described in the sectiondisclosing the linear actuator. Indeed, when the actuator moves itsmovable part (801), the first derivative is greater or less than 0, butwhen the actuator does not move its movable part (801), its firstderivative is substantially equal to 0. In our example, and bypreference, when the magnet (802) moves away from the sensor (803), thefirst derivative is negative and, inversely, when the magnet movescloser, the first derivative is positive.

The system can additionally comprise a mathematical model fordetermining when the movable part moves and when it remains immobile.This second mathematical model takes account of the second derivative ofthe absolute value. By virtue of this second mathematical model, thesystem knows when the movable part changes its behavior (movable orimmobile).

In one embodiment, the control system comprises an actuator comprisingat least one ramp and at least one threshold (for example a linearactuator of the kind described in the present document), and a processoradapted to control the actuator and to process the signal according toat least one mathematical model.

A first mathematical model takes account of the first derivative of theabsolute value measured by the sensor (803). The processor can use thisfirst mathematical model in order to establish in which direction themovable part (801) moves. When the first derivative is close to 0, thecontrol system knows that the actuator has reached a threshold.

A second mathematical model takes account of the second derivative ofthe absolute value measured by the sensor (803). The processor can usethe second mathematical model in order to establish when a threshold isreached and/or when the movable part is immobile or moving. The lowergraph of FIG. 33 shows the signal resulting from the second mathematicalmodel. When the signal is equal to the value f, this signifies that theactuator maintains a position or is on a threshold. When the signal isequal to the value d, it signifies that the movable part (801) ismoving. Thus, by virtue of this second mathematical model, the systemhas no need of the absolute value. When the control system powers theactuator in order to move its movable part (801), the secondmathematical model makes it possible to establish when the actuator hasreached a position. In other words, when the actuator continues itsactuation (for example it causes the bearing means (209) to turn) butthe movable part no longer moves, the processor, by virtue of the firstand/or second derivative, is able to establish that the bearing meanshas reached a threshold. Thus, when the processor orders a change ofposition of the actuator, a mathematical model allows the processor toknow when the threshold is reached and it thus orders the actuator tostop.

Thus, said control system is adapted to determine at least one positionreached by the movable part (801) of the actuator independently of thecharacteristics of the sensor used. Said control system is adapted tostop the actuator at at least one position reached by the movable part(801) of the actuator independently of the characteristics of the sensorused.

In one embodiment, the control system comprises an actuator comprisingat least two separate positions. The actuator comprises at least onethreshold defining a position, and at least one ramp making it possibleto change position. The actuator is driven by a motor designed to turnpreferably in a single direction, such that it goes from one position toanother sequentially and in a pre-defined order. Preferably, theactuator is adapted to return to its starting position by executing atleast one partial revolution. In addition, the processor comprises amathematical model that takes account of the second derivative of theabsolute value measured by said sensor. Said processor comprises amemory which contains the sequence of the positions, such that saidsystem does not need to know the first derivative of the absolute valuein order to know the position of the actuator. It suffices for theactuator to execute one revolution in order to know with precision itsposition, for example during the start-up of the system.

Drive Device used for the Peristaltic Pumps:

In one embodiment, the treatment system can comprise a drive device usedfor the peristaltic pumps. Said drive device disclosed by the presentdocument can also be used by diverse peristaltic pumps and/or fluiddistribution systems comprising a peristaltic pump.

The invention also discloses a method for correcting the toleranceerrors of the shaft driving the peristaltic pumps. Said invention,presented in FIGS. 22 and 23, is a drive device (300) which comprises afloating shaft (301) driven by a drive means (303) fixed to a rotor(310) of an electric motor (not shown). Said floating shaft (301)comprises a rigid assembly of base (311) and cover (302) forming acavity inside which said drive means (303) is at least partiallycircumscribed. Said drive means (303) comprises a rigid body designed insuch a way as to cooperate with the walls (309, 309′) of said cavity(313), so as to permit a limited freedom of the floating shaft (301)with respect to the axis of said rotor (310). A screw (307) can permitfixing of the drive means (303) to said rotor (310).

The cavity comprises at least one cooperation element (312), whichallows said drive means (303) to transmit a rotation movement to saidfloating shaft.

Preferably, said cooperation element (312) is an opening limited by twohard elements (308) and through which a shaft (306) is housedperpendicularly. The space between the two hard elements (308) isreasonably greater than the diameter of the shaft (306).

The hard elements (308) and/or the shaft (306) can be made from hardmetals such as cobalt, tungsten, vanadium, chromium, manganese, nickel,titanium, germanium, gallium, bismuth, indium, lithium, magnesium,molybdenum, strontium, rubidium or palladium. In one embodiment, thehard elements (308) have a greater hardness than the shaft (306). Thehard elements (308) and/or the shaft (306) can be treated to increasetheir hardness, for example with zirconium oxide or one of its alloys.

In one embodiment, the body (304) of said drive means (303) can be of aspherical shape that is perfectly round or partially flattened. Inanother embodiment, said body (304) forms a roller comprising threefaces. Two of the three faces lie opposite each other and areinterconnected by way of the third face, which is curved. On the planeX-Z, said roller forms a circle formed by said curved face. Theconnection between at least one of the two faces lying opposite eachother and the curved face can be rounded on the plane X-Y. The faceslying opposite each other can be substantially plane and/orsubstantially parallel with respect to each other.

In one embodiment, the cavity (313) comprises three smooth walls (309,309′). Preferably, the upper wall (309) and/or the lower wall (309′) ofsaid cavity (313) are of at least partially conical shape. The surfacesof the upper wall (309) and of the lower wall (309′) can be plane orcurved.

In one embodiment, on the plane X-Y, the cone of the smooth wall (309)is defined according to an angle of between 0 and 90°, preferably ofbetween 5 and 30°. The cone of the opposite smooth wall (309′) isdefined according to an angle of between −0 and −90°, preferably ofbetween −5 and −30°. The angles of the two partial cones can be equal ordifferent.

The smooth walls (309, 309′) are adapted to cooperate with the ends ofthe body (304) such that the floating shaft (301) can move on at leastthree axes X, Y or Z and/or can undergo pitching movements. For example,on the axis Y, the floating shaft (301) can undergo a pitching movementof +/−10°, preferably of +/−5°.

In one embodiment, the drive means (303) comprises a longitudinal shaft(305) and the floating shaft (301) comprises a second cavity (313′),which extends along the floating shaft. The longitudinal shaft (305)fits inside the second cavity (313′) in order to restrict the pitchingmovements of the floating shaft (301). Generally speaking, andpreferably, the dimensions of the elements forming the drive means (303,306, 305) are reasonably smaller than the elements forming the inside ofthe floating shaft (301, 302, 313, 312).

In one embodiment, the drive system (300) comprises a drive shaft whichis formed in one piece, extends on the axis Y and is adapted to drive atleast one roller (320) of a peristaltic pump system. said roller isadapted to crush a flexible tube (not shown) against a wall (not shown).According to FIGS. 22 and 23, the drive shaft is represented by thefloating shaft (301). In other words, the drive shaft can be thefloating shaft and/or merged with a part of the drive system. Accordingto FIGS. 22 and 23, the drive shaft can be of cylindrical shape andcomprise a beveled free end (here the term free end is the opposite ofthe opposite end connected directly or indirectly to the motor). Thecylinder of the drive shaft forms a circle on a plane X-Z.

In one embodiment, said drive shaft is formed in one piece composed ofat least two different cylinders that are defined by the same axis (inother words center of the cylinder) but have different diameters. Thus,on the plane X-Z, the drive shaft can form at least two circles that areparallel but of different sizes. In addition, the drive shaft cancomprise three cylinders of which one alone is of a different diameter.The cylinder defined by the smallest diameter can be arranged betweenthe two cylinders of equal diameter. Said cylinders of greater diametercan have surfaces that are treated in such a way as to improve thecooperation with the rollers of the peristaltic pump.

This construction of the drive shaft with three cylinders isparticularly suitable and of advantage for the use of an H-shapedroller, such as the roller (320) of FIG. 23. The roller is arranged in aperistaltic pump system and will crush a flexible tube. The function ofcrushing is preferably effected by a rigid part (322) of the roller(320). Said roller (320) is a cylinder forming a circle on the plane X-Zand comprises a shaft (321) at the center of this cylinder that extendson the axis Y, a rigid part (322), and at least one flexible part (323)which is deformable. The flexible part is adapted to cooperate with thedrive shaft.

Preferably, the cylinders of greater diameter come into contact with theflexible parts (323) of the roller (320) and drive the roller (320).When the drive shaft is in contact with at least one flexible part, saidflexible part (323) can deform in order to improve the cooperationbetween these two elements and/or to adjust the tolerance errors of eachof these elements.

Preferably, the roller comprises a rigid part (322) at its center andtwo flexible parts (323) at the ends on the axis Y.

A fluid distribution system comprising a floating shaft (301), a driveshaft with three cylinders and/or a roller with rigid and flexible partsmakes it possible to substantially improve the cooperation betweenroller and drive shaft and to correct the tolerance errors of thevarious elements of the system.

Means for Damping the Pressure Peaks:

In one embodiment, the treatment system comprises at least one means fordamping the pressure peaks.

FIG. 24 shows the pressure signal measured near the inlet of aperistaltic pump. On the first curve (401), it is possible to observethe oscillation of the pressure, while the second curve (402) representsthe mean value of this pressure. The aim of the damper is to reduce theamplitude of the oscillations of the first curve (401).

Such a damping means can be installed in one or more flow paths of adistribution system as described above. Preferably, this damping meansis integrated in a cassette.

Whether in peritoneal dialysis or continuous renal replacement therapy,each treatment has one or more possible configurations. The phenomenonof pressure peaks can be amplified or attenuated by various elementsthat vary according to said configurations. It will be recalled that oneof the objects of the invention is to permit simple use of the system.Therefore, reproducibility is an important element, since the operator(generally the nurse) must be able to ensure correct operation of thesystem without having to take into account the characteristics of thedifferent elements.

The distribution system as disclosed in this document is a cassettethrough which fluids flow in three flow paths. Preferably, they arepropelled by peristaltic pumps. Reproducibility, precision and patientcomfort are important elements. Thus, at least one damping means ispreferably integrated in said cassette. To be as effective as possible,said damping means must be placed as close as possible to the pumpingsystem.

In an embodiment depicted schematically in FIG. 25, the flow pathcomprises walls (404) delimiting said path. These walls can be the rigidwalls of the cassette. A section of the flow path is covered by aflexible membrane (403), which then replaces said wall (404). By virtueof the elasticity of said flexible membrane (403), the pressure peaksare substantially attenuated, absorbed by the deformation of themembrane (403). The absorption of these peaks depends on the size andelastic characteristics of the membrane.

In another embodiment, depicted schematically in FIG. 26, the flow pathlikewise comprises walls delimiting said path, but a section is replacedby a cavity filled with a compressible fluid such as air. This air mayhave been trapped (about 1 ml) during the priming of the system. Thus,the volume of the air is compressed to a greater or lesser extent duringthe pumping, absorbing the energy of the pressure peaks. This embodimentis particularly effective since it requires little energy for itsoperation, and said fluid very rapidly absorbs the pressure peaks.Preferably, the cavity or the inlet of the cavity is designed to avoidthe compressible fluid completely escaping. In other words, the cavityis designed to ensure that the flowing fluid does not replace thecompressible fluid.

Preferably, said damping means is placed upstream of the pumpingmechanism.

The invention claimed is:
 1. A medical pump system comprising: adisposable cassette having a pump; and a reusable apparatus having adrive device configured to cooperate with the pump of the disposablecassette, wherein the drive device includes a floating shaft having arotational axis rotatably driven by a drive means, the drive meansconfigured to be coupled to a motor rotor having a motor axis of thereusable apparatus, wherein the floating shaft includes a cavity insidewhich the drive means is at least partially circumscribed, wherein thedrive means includes a body configured to cooperate with internal wallsof the cavity to limit an orientational freedom of the rotational axisof the floating shaft relative to the motor axis to compensate fortolerance errors of the pump, and wherein the cavity includes acooperation element allowing the drive means to apply a rotationmovement to the floating shaft.
 2. The medical pump system as claimed inclaim 1, wherein the body of the drive means includes smooth roundededges and the cavity includes smooth walls.
 3. The medical pump systemas claimed in claim 1, wherein the drive means includes a longitudinalshaft, and the floating shaft includes an additional cavity extendingalong the floating shaft, the longitudinal shaft located inside theadditional cavity to limit lateral movements of the floating shaft. 4.The medical pump system as claimed in claim 1, wherein the drive meansincludes a transversal shaft, and the cooperation element includes twohard elements, wherein the transversal shaft is configured to engagewith the two hard elements of the cooperation element for applying therotational movement.
 5. The medical pump system as claimed in claim 4,wherein at least one of the hard elements of the cooperation element andthe transversal shaft of the drive means is made of a compositionincluding an element selected from the group including cobalt, tungsten,vanadium, chromium, manganese, nickel, titanium, germanium, gallium,bismuth, indium, lithium, magnesium, molybdenum, strontium, rubidium,and palladium.
 6. The medical pump system as claimed in claim 1, whereinthe internal walls of the cavity are configured to cooperate withexternal walls of the body of the drive means to allow the floatingshaft to move linearly relative to the drive means.
 7. The medical pumpsystem as claimed in claim 1, wherein the internal walls of the cavityare configured to cooperate with external walls of the body to allow therotational axis of the floating shaft to undergo pitching movementsrelative to motor axis between +/−10°.
 8. The medical pump system asclaimed in claim 1, wherein the internal walls of the cavity areconfigured to cooperate with external walls of the body of the drivemeans to allow the rotational axis of the floating shaft to undergopitching movements relative to the motor axis between +/−5°.
 9. Themedical pump system as claimed in claim 1, wherein the internal walls ofthe cavity includes a cone shape having a cone angle of between 0° and90°.
 10. The medical pump system as claimed in claim 1, wherein theinternal walls of the cavity includes a cone shape having a cone angleof between 5° and 30°.
 11. The medical pump system as claimed in claim1, wherein the pump includes a peristatic pump including a flexible tubeand a roller, the floating shaft configured to operationally engage withthe roller of the peristaltic pump.
 12. The medical pump system asclaimed in claim 11, wherein the roller includes a flexible partconfigured to cooperate with the floating shaft.
 13. The medical pumpsystem as claimed in claim 1, wherein the floating shaft includes arigid assembly having base and a cover, the cover forming the cavity.14. The medical pump system as claimed in claim 1, wherein the drivemeans includes a transversal shaft, and the internal walls of the cavityinclude two walls arranged above and below the transversal shaft, thetwo walls having a conical shape.
 15. A medical pump system comprising:a disposable cassette having a pump; and a reusable apparatus having adrive device configured to cooperate with the pump of the disposablecassette, wherein the drive device includes a floating shaft having arotational axis rotatably driven by a drive means, the drive meansconfigured to be coupled to a motor rotor having a motor axis of thereusable apparatus, wherein the floating shaft includes a cavity insidewhich the drive means is at least partially circumscribed, wherein thedrive means includes a body configured to cooperate with internal wallsof the cavity to limit an orientational freedom of the rotational axisof the floating shaft relative to the motor axis to compensate fortolerance errors of the pump, and wherein the internal walls of thecavity are configured to cooperate with external walls of the body toallow the rotational axis of the floating shaft to undergo pitchingmovements relative to motor axis between +/−10°.
 16. A medical pumpsystem comprising: a disposable cassette having a pump; and a reusableapparatus having a drive device configured to cooperate with the pump ofthe disposable cassette, wherein the drive device includes a floatingshaft having a rotational axis rotatably driven by a drive means, thedrive means configured to be coupled to a motor rotor having a motoraxis of the reusable apparatus, wherein the floating shaft includes acavity inside which the drive means is at least partially circumscribed,wherein the drive means includes a body configured to cooperate withinternal walls of the cavity to limit an orientational freedom of therotational axis of the floating shaft relative to the motor axis tocompensate for tolerance errors of the pump, and wherein the internalwalls of the cavity includes a cone shape having a cone angle of between0° and 90°.